1. Field of the Invention (Technical Field)
The invention relates to the medical application of radiation and more particularly to a method and apparatus for the production via low energy nuclear reactions and delivery of radiation via a conduit-needle or tube to a treatment site.
2. Background Art
Radiotherapy and radiosurgical techniques allow a surgeon to kill diseased tissue in a body with little or no operative intrusions. Ideally, the aim of medical radiation therapy is to deliver a lethal dose of radiation to a clearly defined region of diseased tissue while inflicting little or no radiation damage on surrounding healthy tissue. However, the delivery of radiation to the diseased tissue almost always involves some transport of the incident radiation across healthy tissue which also suffers damage.
The existing techniques for delivering radiation to a region of diseased tissue are proton radiotherapy and radiosurgery, brachitherapy, laser ablation, x-ray irradiation, boron neutron capture therapy (BNCT), electron beam irradiation, gamma-ray knife, and the like.
Proton radiotherapy (PR) delivers radiation to the site of a tumor along a straight-line from outside the body. The incident proton beam interacts directly with the intervening tissue, producing radiation damage along its path to the tumor. Therefore, in many instances, in order to avoid excessive damage to healthy tissue fractionated treatments are necessary, further increasing the cost of treatment and increasing the use of facilities for additional treatment sessions.
The implementation of PR treatments require accelerator facilities to produce the radiation. The 50 to 200 MeV protons necessary for PR are produced by cyclotrons or linacs in facilities costing up to a hundred million dollars and containing significant supporting infrastructure.
The temporary implantation of naturally occurring radioisotope sources at the site of a cancerous tumor, brachitherapy, is also an accepted and frequently used mode of radiation therapy. It entails the insertion of radioactive source material usually in the form of a needle or beads, to the site of a tumor. Once inserted, the source of radiation resides within the body, thus avoiding to a large extent, exposure of healthy tissue to needless irradiation. However, the radiation sources cannot be turned-off, must be stored and handled with extreme care, and exposure geometries and durations must be very accurately determined.
The destruction of cancerous tissue through the use of directed, high-intensity laser light, or laser ablation, is also an existing radiation treatment technique. However, while the laser light can be delivered to the tumor through a flexible conduit, has a self-limiting range of penetration, and poses no danger when turned off, the use of laser irradiation to destroy the tumor also results in scarring of the treated area since there is no opportunity for the re-emergence of healthy tissue. Thus, for dermatological applications, laser treatment of the tumor often results in permanent damage to the appearance and/or function of the host organ.
A significant advantage inherent in proton or deuterium radiotherapy arises from the enhanced radiation doses that can be achieved at a tumor site when the beam energy is tuned so that the ions come to rest at or near the tumor. This enhancement, which is simply a consequence of the position of the Bragg peak (i.e., the maximum) in the proton or deuterium stopping power curve shown in FIG. 1, is a considerable improvement over dose distributions achievable with x-ray or electron irradiations. Unfortunately, the damage done along the incident path of the beam, while much reduced using deuterium or proton beams, can still be as much as 30% of that delivered to the site of a tumor and therefore contributes to the production of damage in healthy tissue. This incidental radiation damage can, at best, limit the deliverable dose for any one exposure, thus requiring repeated treatments at sub-lethal doses so that the damaged healthy tissue can recover before the next treatment, and at worst, can result in the destruction of healthy tissue. It has been noted that large tumors are less likely to be cured at doses of radiation that are still within the tolerance of adjacent normal tissue. Normal tissue sparing is enhanced when (a) the volume of irradiated normal tissue is reduced and (b) the biologic effect on tumor cells is greater than that on surrounding normal cells. These two factors must be optimized to improve the probability of an uncomplicated cure.
By using the products of low energy, ion-induced nuclear reactions for radiation therapy applications, namely ion-induced nuclear radiotherapy or INRT, these factors can be optimized so as to allow arbitrarily large doses of radiation to be delivered, in a single exposure, to a highly localized region of tissue, while inflicting little or no collateral damage on surrounding healthy tissue. Such a form of radiosurgery with clear, pre-defined dose boundaries provides increased precision in controlling the irradiated region and removes many existing constraints on the deliverable dose.
U.S. Pat. No. 1,720,019 to Hart describes a device for transmission of ultraviolet (UV) radiation produced by an external source into the interior of a living body via a liquid medium held in a tube inserted into the body. The tube may also be used to inject the same liquid medium into the area under treatment. Although, Hart indicates all forms of radioactive energy can be used, the description is limited to UV radiation. The Hart device uses the incident radiation itself for destroying living tissue and not the by-products of low energy, nuclear reactions created at the end of the tube to produce the radiation. Finally, Hart's UV radiation is limited to destroying tissue in the line of sight of the inserted device.
U.S. Pat. No. 1,939,413 to Robinson, describes a device specifically intended to irradiate the interior surface of the urethra and bladder with ultraviolet light. Additionally, there are provision made for the draining and injection of fluids into the bladder. The short comings of Hart are also present in this device, in that the UV radiation is limited to destroying tissue also in the line of sight of the device. Additionally, there is no disclosure for the use of a combination of a radiation and thermal treatment to destroy diseased tissue.
U.S. Pat. No. 3,589,353 to Banko et al describes a hollow, ultrasonic vibration device intended to break up and remove animal tissue. In Banko, physical contact between the rapidly vibrating tip and the target tissue results in disintegration of the target material into minute particles which are then flushed from the operating region by fluid from the device tip and suctioned away by another tube within the device tip. Banko does not disclose the deposition of energy via charge particle radiation and heat to destroy diseased tissue.
U.S. Pat. No. 4,207,874 to Choy describes a device intended to clear up obstructions in tubes using a bundled arrangement of optical fibers to provide illumination, imaging and laser ablation of obstructions in its path, and a hollow suction tube to clear the ablated material from the tube. Choy discloses a laser beam propagated down a solid optical fiber to the intended target. Choy further discloses a method to create localized heating and vaporization of obstructing tissue. The only tissue that is destroyed is the tissue that is directly in the laser's path. Choy also does not disclose irradiating and destroying tissue in a volume defined by the range and angular-dependence of the emitted charged particles from a nuclear reaction.
U.S. Pat. No. 4,781,198 to Kanabrocki describes a device to facilitate the accurate positioning of a biopsy needle within a body. The device relies on coating the tip region of a biopsy needle with a gamma-ray emitting material which can be viewed in real time on a scintillation scope during the positioning of the needle. The Kanabrocki device is solely intended for positioning the biopsy needle and does not serve a therapeutic purpose.
U.S. Pat. No. 4,976,680 to Hayman describes a device to facilitate the accurate positioning of radioisotope sources within a body so as to deliver maximized radiation doses to a tumor while minimizing both the exposure of healthy tissue and related surgical procedures in handling the radioactive sources. The apparatus relies upon the use of a set of hollow tubes which are inserted into the patient, terminating in and around the tumor area. Radioisotope sources, in the forms of wires, are then guided down the tubes to the appropriate positions within the tubes in order to deliver maximum radiation dose to the tumor with a minimized dose to healthy tissue. This is a modified form of brachitherapy in which the radioactive source material is not directly handled by the surgeon, but is rather positioned along a fixed path defined by the inserted tubes.